The present invention relates to the manufacture of a twisted nematic field effect mode liquid crystal display cell.
Heretofore, a twisted nematic field effect mode liquid crystal display cell was generally manufactured by one of the following two methods:
(1). A transparent insulating film was formed, through the use of evaporation techniques, on a glass substrate with transparent electrodes formed thereon in order to uniform the hardness of the surface of the glass substrate and protect the transparent electrodes from the surrounding environment. Then the surface of the transparent insulating film was rubbed with the use of a polishing cloth to form micro-grooves aligned in a predetermined direction. The thus formed two glass substrates were spaced from each other by a distance of about ten micrometers (10 .mu.m) in such a manner that the alignment directions on the respective glass substrates were orthogonal to each other and sealed through the use of epoxy resin. The space between the substrates was then flled with liquid crystal compositions.
(2). A transparent insulating film was formed, through the use of evaporation techniques, on a glass substrate with transparent electrodes formed thereon in order to uniform the hardness of the surface of the glass substrate and protect the transparent electrodes from the surrounding environment. Then micro-grooves aligned in a predetermined direction were formed through the use of silicon oxide tilted evaporation techniques. The thus formed two glass substrates were then spaced from each other by a distance of around ten micrometers (10 .mu.m) in such a manner that the alignment directions on the respective glass substrates were orthogonal to each other and sealed through the use of low melting sealing glass. Liquid crystal compositions were then filled in the spaces between the substrates.
A hermetic seal using the low melting sealing glass is superior to a sealing method using epoxy resin, because the hermetic seal can prevent moisture invasion. Moisture will increase the conductivity of liquid crystal composition and will promote chemical deterioration of a liquid crystal composition.
The rubbing ethod discussed hereinbefore is superior to the silicon oxide tilted evaporation technique because silicon oxide tilted evaporation is not suited for mass production since it is difficult to use an evaporation source of a large size.
However, in the mechanical rubbing method a glass paste used with the low melting sealing glass will generate organic elements during the heat seal operation, the organic elements damaging the alignment formed on the transparent insulating film by attaching to its surface when the alignment is effected. Therefore, in the prior art, the alignment was effected through the use of silicon oxide tilted evaporation techniques when low melting sealing glass was used for sealing the twisted nematic field effect mode liquid crystal display cell.
Accordingly, an object of the present invention is to provide a method of manufacturing a twisted nematic field effect mode liquid crystal display cell suited for mass production.
Another object of the present invention is to combine a hermetic seal with the mechanical rubbing method in fabricating twisted nematic field effect mode liquid crystal display cells.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
To achieve the above objectives, pursuant to an embodiment of the present invention, a transparent insulating film having a low adsorption characteristic of organic elements such as silicon dioxide is formed on a glass substrate with transparent electrodes formed thereon. The surface of the transparent insulating film made of silicon dioxide is mechanically rubbed through the use of a polishing cloth or felt in order to form micro-grooves aligned in a predetermined direction. The organic elements generated from the glass paste during the low melting glass sealing operation will scarcely adhere to the surface of the transparent insulating film made of silicon dioxide and, therefore, the alignment will not be damaged.